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smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=PM53I5cc; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CDEEA606A319 for ; Wed, 21 Oct 2026 08:28:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=PM53I5cc Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3E3051F000CA; Wed, 21 Oct 2026 08:27:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1792571281; bh=j31Wa+4Xf0QQi5l0YauHX7WiMP7itq7ljmmvwGJrI04=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=PM53I5cc33ohdAjMTn0Uf70/koVDQJId9SXhNgrzvyHoQ5uH+/rGSI/nTuEG5RoNz udGMlFW3HYIlwcK2oNmsvavkXhxbnjFC14MirI+Veow+/hPQ4myfQPbLxwVI/zBOqx 9iqTuqLrYwWlxGbsB5uRE1Uxfi7UV/+uOZ1EoYkwquIiZvv3HK5mujkfojeCsuF//7 mFmD7b1tk6hbEIUt8HSU0Llv0RHdvDXgN+4lvXrFsSBinD87FnMRdxApxuiOH91akE UsfN12Z3nKK4+gCOoYjdMBIC8/3kTmH7KOdEzmTZrAgcXSplXrKCz+XzDpp6uvsP/+ lkRxHk+ZribPQ== Message-ID: Date: Wed, 21 Oct 2026 10:27:55 +0200 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/2] mm/compaction: skip folios containing hwpoisoned pages To: Kaitao Cheng , "Huang, Ying" , Yuanhe Shu Cc: akpm@linux-foundation.org, vbabka@kernel.org, linmiaohe@huawei.com, nao.horiguchi@gmail.com, ziy@nvidia.com, wangkefeng.wang@huawei.com, tujinjiang@huawei.com, mgorman@techsingularity.net, chengkaitao@kylinos.cn, muchun.song@linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20260928105805.1215770-1-xiangzao@linux.alibaba.com> <20260928105805.1215770-2-xiangzao@linux.alibaba.com> <99cbd960-439d-4672-aba9-6b49697db8b3@kernel.org> <20260929034123.2705745-1-xiangzao@linux.alibaba.com> <877bjowf9i.fsf@DESKTOP-5N7EMDA> <23d3756c-1a87-402d-80b4-c838dfc29f4d@linux.dev> <9da90d76-031f-4211-b9de-439cbf7bc63d@kernel.org> <49966df8-c092-40de-a05a-ff6d69382dd4@linux.dev> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 8bit On 10/21/26 04:49, Kaitao Cheng wrote: > > > 在 2026/10/20 21:58, David Hildenbrand (Arm) 写道: >> On 10/20/26 15:31, Kaitao Cheng wrote: >>> >>> >>> 在 2026/10/20 21:07, David Hildenbrand (Arm) 写道: >>> >>> It does require architecture support, but that doesn't seem practical, haha. >> >> Well, but that's required when an arch wants to rule out all races. >> >>> >>> >>> Do we need to check both before and after the copy? This feels a bit >>> redundant, and I'm not sure whether such a small race window warrants >>> an additional check. >>> >> >> I don't see how checking after the copy makes any sense? :) >> >> You already crashed if there was a problem, why check? Or what am I missing? > In cases such as transient errors, software poison injection, repeated > bit flips in memory, or bit flips in the ECC check bits themselves, a > page may be faulty while memcpy() still completes normally. If the copied > data is correct, only the PG_hwpoison flag is lost during migration. But > if the copied data is corrupted and the kernel or a process subsequently > treats it as valid, I think the consequences could be more serious than > an immediate crash. However, I cannot estimate how likely this is to happen. That's the point, me neither. I'm happy to perform checks before access, or after, in the default copy implementation, but I want to have properly documented how this makes sense and which races exist. -- Cheers, David